THE MYRIAD FASCINATIONS OF FLAT TOP HILL

Forest and Bird, Issue 268, 1 May 1993, Page 20

THE MYRIAD FASCINATIONS OF FLAT TOP HILL

NEVILLE PEAT

The Department of Conservation has acquired the northern end of Flat Top Hill — a representative piece of Central

Otago dryland.

reports on the wonderful diversity of the plant and animal life of this new

conservation. asset.

LAT TOP HILL is a bulging foothill of the Old Man Range -a "dry, whale-backed hummock of a hill’, as one scientist put it. Eleven kilometres long and 813 hectares, it separates the Fruitlands district south of Alexandra from a canyon cut by the Clutha River, now the dammed upper reaches of Lake Roxburgh.

In the wider context of Central Otago’s block mountain and range-and-basin landscape, Flat Top Hill is a relatively minor event — a kind of block mountain in miniature. To the uneducated eye the landscape might appear a parched wasteland, good for nothing, not even sheep these days. But there is more here than meets the eye. Flat Top Hill has carved itself an ecological niche. Notwithstanding the fact this is about the driest place in New Zealand (rainfall averages less than 350 mm or 13.7 inches a year), scientists have counted 180 native vascular plant species. In terms of biological diversity — a catch phrase at the Earth Summit at Rio

de Janeiro last year — this place is a gem. Some of New Zealand’s tiniest plants — most of them regional endemics — live here. On the salt, wind-eroded soils beside Butchers Dam on the western side of the hill, a native forget-me-not, Myosotis pygmaea var. minutiflora, tarns on a miniature flower show for a few weeks in spring. Two other tiny spring annuals, long in name but short in stature — Myosurus minimus novae-zelandia and Ceratocephalus pungens are considered endangered. The type locality for Ceratocephalus has been converted to pasture. All three spring annuals occur together and separately at Flat Top Hill, forming distinctive communities, found nowhere else, with other salt-tolerant species. From Butchers Dam at 140 metres above sea level, the land rises to 550 metres. It is classic Central Otago. The higher ground is studded with outcrops of decaying schist that tease the imagination with weird angles and shapes. At the foot of the hill, beside Butchers Dam, the

characteristic grey and brown shades of the earth give way to splashes of vivid colour — red, orange, yellow, and dazzling white. The colours are contained in a sequence of ancient soils. Known as paleosols, these soils were formed 20 to 25 million years ago, apparently in a tropical or sub-tropical climate, and remained buried under sedimentary layers until the gold miners arrived. The soils were exposed by alluvial gold-mining operations that sluiced away the sedimentary material. From the shores of the dam to the flats at the summit, the area contains a range of habitats, including salty ground, short tussock grassland, shrubland, cushion fields and an occasional seepage or wet zone. There is a pond on top of the hill, seasonally dry. The salty soils harbour plants found in only a few other places. Not surprisingly, the diverse habitats are host to a variety of insects and other invertebrates. The rare flightless Alexandra chafer beetle lives here. So does a broad-nosed

weevil that appears to be new to science. Brightly coloured day-flying moths frequent the warm surfaces of the tors. Like many properties in the region, this one has had its share of rabbits. Local farmers probably thought DoC was buying a headache. But a poisoning programme last year made inroads into the rabbit population and there has been follow-up shooting through the first half of this year.

DoC closed the area to the public for a few months to minimise disturbance to the rabbits and encourage them into open spaces where they would become easier targets. The other scourge of the range lands, Hieracium, has had little impact at Flat Top Hill. Wilding pine trees are a potential threat, however, and DoC has plans to remove these before they become a problem. On the sloping lower areas, introduced thyme blankets the ground, filling the air with its savoury scent, but it is not considered a threat to natural values in the long run. DoC scientist Brian Patrick organised a

recent visit to Flat Top Hill by a party of botanists, two of whom were from the North Island. They were delighted by their finds, which included several undescribed vascular plants. Dr Geoff Rogers, a specialist in nonforest vegetation from Landcare Research in Rotorua, took a guess at what would happen to this landscape after 50 to 100 years of protection. He thought it would develop into a kanuka woodland with kowhai trees and shrubs such as Cassinia, Olearia and Coprosma mingling with the groves of kanuka. On the higher ground, native short tussock (Poa and Festuca), together with Cassinia would probably dominate. 6 6 HERE’S NO DOUBT," says Brian Patrick, "that Flat Top Hill is nationally important in a conservation context.

There’s nothing quite like it." In addition to the natural values, the area is of interest historically. On

the eastern side, near the shores of Lake Roxburgh, there are several rock shelters that were occupied by miners last century and as recently as the 1930s. One shelter has been converted into two rooms by the use of rock walling. The fact that many such gorge shelters have been drowned by hydro-electric development makes the examples surviving at Flat Top Hill all the more important. In Central Otago there are precious few places like Flat Top Hill where people can freely roam and experience the dryland environment first-hand. Central Otago has very few protected areas at relatively low altitude. Most of the reserves are on the tops of the ranges — the Bain Block on Old Man Range, for example, and the reserve on the summit of the North Dunstan Mountains. Flat Top Hill has always been Crown land, leased for grazing. Its conservation value was recognised only in the past few

years. DoC bought the run for $68,000, including payments of $45,000 to the lessee and $21,000 to Landcorp. A small amount went towards the settlement of outstanding pest rates. ’ For the time being the area will retain the status of stewardship land. The site’s proximity to State Highway 8 is bound to make it a popular attraction in the future and DoC has plans eventually to establish signposted walking tracks that will give visitors a look at a range of habitats. Views from the summit are spectacular, taking in the Old Man Range, Dunstan Mountains and Manuherikia Valley. And yet, notwithstanding the panoramas, Flat Top Hill is certain to attract, in spring at least, visitors intent on examining the ground on hands and knees, hoping for a peek at the miniature plants -a forget-me-not experience.

Neville Peat is a writer based in Dunedin. His latest books are The Falcon and the Lark and Stewart Island: the last refuge.